The key is developing new varieties of food that are easier for cattle to digest and also provide a proper balance of fibre, protein and sugar, said Michael Abberton, a scientist at the UK-based Institute of Grassland and Environmental Research.

This could open up plant-based solutions as alternatives to reducing stock as farmers look for ways to cut methane emissions amid warming climates, he told a briefing on farming and climate change at London's Science Media Centre.

He noted the average dairy cow belches out about 100 to 200 litres of methane each day, making diet changes a key potential factor in reducing this greenhouse gas.

"There is a common misperception about how methane gets into the atmosphere," he said. "It is actually through belching rather than the other end."

Agriculture is responsible for about seven percent of UK greenhouse gas emissions and a large proportion of two of the most potent gases with 37 percent of methane and 67 percent of nitrous oxide.

Greenhouses gases are widely blamed for causing global warming. Scientists say average temperatures will rise by between two and six degrees Celsius by the end of the century, causing droughts, floods and violent storms.

Abberton said introducing easier-to-digest legumes that tend to reduce methane emissions is an example of an approach scientists are beginning to explore. Legumes such as clover and alfalfa are commonly used for animal fodder.

It also requires farmers to balance cows' legume intake with other food and to develop different species of grass that are also more digestible, he added.